The present invention relates to improvements in mechanisms and method for the preparation of stock for papermaking machines, and more particularly to a system for the removal of tramp reject materials from acceptable fibers.
In tramp reject removal systems heretofore available, air nozzles have been employed which incur a high fiber loss which is obviously undesirable. These have proven no more efficient than other systems which employ floating velocity arrangements for the removal of tramp materials. In systems now available, the ineffectiveness is caused primarily by the thick burden of material which has to be affected by the nozzled air flow. The nozzle arrangement becomes critical. This is because there is a need to continue forcing or checking material as it twirls, flips and falls progressively downwardly optimizing the separation between the acceptable fibers and the tramp material, such as tramp iron knots and the like. The systems in other industries have utilized a flow of separation air to separate or stratify materials. Examples of these are shown in U.S. Pat. No. 2,828,011 which is designed for the classification of materials such as middling stocks in flour mills wherein airstreams are arranged to separate different grades of material of ground flour. Another example is U.S. Pat. No. 3,384,233 which is designed for the cleaning of sugar cane and uses air flow to separate leafy trash from the stream. The principle of these and other devices using air flow for separation are impractical for the problems faced in the purification or cleaning of papermaking fibers. Such fibers must be free of tramp iron, large knots and other impurities as they are processed and pulped prior to being dewatered and formed into a web and further dried in a papermaking machine.
An object of the present invention is to provide an apparatus and method for the cleaning of papermaking fibers by the removal of tramp reject materials which avoids the disadvantages of systems heretofore used and which avoids unnecessary fiber loss.
A further object of the invention is to provide an improved system employing air injected crosswise into a stream of fibers for the separation of tramp material from usable fibers.
A further object of the invention is to provide an overall improvement in systems preparing pulp for papermaking by the purification or cleaning of fibers with the removal of materials which cannot be tolerated in pulp preparation and paper web forming.